Getting Inkjet Ink and Print Heads to Work Together
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Getting Inkjet Ink and Print Heads to Work Together

Inkjet print systems fail primarily because of the fluids used in them. Read on to find out if it's all a hoax or if putting high-test in is all it's cracked up to be.

By Vince Cahill, President, VCD Solutions

Inkjet print systems fail primarily because of the fluids used in them. The inkjet process requires the use of inks and chemicals that will perform within narrow tolerances of small print head fluid channels. Some solvents and chemistries can destroy print heads. Some will tolerate aqueous fluids while others will not. Some will tolerate true solvent while others will not.

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  • Specific print heads will require the fluids put through them to have specific characteristics and limited tolerances for variation. Print head manufacturers have a vested interest in insuring the fluids used in their products perform optimally, since the success of their products’ performance depends on them. Some print head suppliers control which inks and chemicals will be used in their devices through licenses with OEMs that use their heads. Others will certify inks to work in their devices.

    Inkjet printing is far more complex and delicate than analog printing. Inkjet printing requires the nozzles to fire precisely sized drops with exact straightness and accuracy, many thousands to hundreds of thousands of times per second. Inkjet printer manufacturers must integrate complex and highly refined elements in order to produce the desired images or fluid deposition. These elements include print heads, electronic controllers, ink and fluid chemistry, chemistry delivery systems, substrate and coating chemistry, motion control, ink drying and curing, software and post-print processing. All of these elements must work together to produce the intended results.

    Equipment OEMs draw on the capabilities of other companies to create integrated solutions. Drop-on-demand piezo inkjet (PIJ) and thermal inkjet (TIJ) print heads dispense fluids through extremely small nozzles, and target these drops to fly through a distance as small as a fraction of a millimeter — but more typically 1.5 mm to 5 mm. Some of these systems also can generate multiple wave pulses, which eject droplets that merge in mid-flight from less than 1 mm to as much as 6 mm and deposit at specific locations.

    The deposited fluids then normally have to change from a liquid to a solid, or be adsorbed into the substrate without necessarily drying, as is the case of oil-based inks. Each type of inkjet print head will have its peculiar requirements for ink to perform optimally. Some print heads are designed to use inks with low viscosity (3-4 cP) while others perform best with higher viscosity (8-12 cP) fluids. Still, others can effectively shoot higher viscosity fluids (13-25 cP).

    The water in water-based inks and the solvent in solvent-based inks evaporate or adsorb into a receptive substrate. Substrates and substrate coatings could micro-encapsulate some water-based inks. Inkjet system users want their inkjet fluids to perform successfully, producing the necessary durability, color gamut and fastness to satisfy their applications’ requirements. Since the interactions between inks, print heads and media are critical for this success, ink manufacturers are obliged to make inks that perform in specific print heads for use on particular media.

    While print head manufacturers can attempt to control the fluids used in their products, the printer owner has the legal right to choose the fluids he or she places in them, and may seek less costly alternative chemistries, which have more likely not passed the print head manufacturer’s scrutiny.

    For instance, a UV-curable inkjet user wants to reduce his operating costs. He realizes that he can save up to 50 percent or more on ink costs with Fourth-party inks. For a few weeks, he congratulates himself on the cost savings. Then, a number of his print heads’ nozzles cease operating, and he cannot fulfill customer orders. Or, a user of a solvent inkjet printer switches from the OEM-ink supplier to an off brand and soon cannot reproduce colors, which her customers expect and that the OEM ink could reproduce.

    Another printer adopts Fourth-party ink only to discover that layers of her printer’s print heads have delaminated from each other. Unlike the majority of inkjet users who play it safe and use OEM-supplied inks, these print professionals have traded guaranteed reliability for lower costs. Other cost conscious inkjet users will scrutinize lower cost, ink aftermarket to determine if they can use them without clogging nozzles or destroying print heads while providing the required performance and gamut. Some Fourth-party inks from reputable manufacturers formulate according to the exacting standards, which inkjet print heads require, and can produce acceptable results. Some may even have superior characteristics to certified inks. However, many uncertified inks have caused print heads to fail, resulting in costly repairs and production delays.

    Print head manufacturers will typically certify inks that perform in their products. They have invested in the trained staff and equipment to evaluate ink formulations and determine their compatibility with the print heads. These manufacturers are protecting their reputations and their products’ perceived value. Inkjet users will usually focus on the print head as the source of failure when print heads will not print, even though poorly formulated, defective and damaged inks are more often the culprit.

    A variety of ink conditions can clog, destroy and cause inkjet print heads to misfire and fail to perform. Even OEM inks can fail to perform if they are used beyond their expiration dates, or subjected to extreme heat or cold. Inks have to maintain their performance characteristics for a reasonable period of time while being stored and transported. The reasonable period may vary depending on the time between formulation and use.


    For example, ink manufacturers design commercially supplied pigmented inks to maintain their particulates in suspension for a minimum of six months, which is more commonly for one to two years. Ink formulators design most inks to withstand certain temperature ranges and environmental conditions. Freezing will destroy water-based ink and adversely impact most other inks. Most aqueous-based inkjet systems will not print optimally in high or low humidity environments.

    While Fourth-party ink manufacturers may avoid paying the print head manufacturers for certification, they also forego the cooperation of print head manufacturers who can guide them in formulating inks that will not damage the print heads. A number of Fourth-party ink companies supply ink — which print head companies have not certified — that performs acceptably in print heads. Certified ink suppliers also have started to offer their inks to the aftermarket. End users need to discover the pedigree of the inks they use when evaluating the risks versus the benefits of using Fourth-party inks.

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    Testing for Ink and Print Head Compatibility
    Print head manufactures — such as Brother, Canon, Epson, Fujifilm Dimatix (Spectra), HP, Konica-Minolta, Lexmark, Ricoh, Seiko Instruments Infotech, ToshibaTec and Xaar — test fluid to insure they will not damage their print heads and have them function as intended.

    Dimatix, for example, operates an analytical and materials department (AMD) at its Lebanon, New Hampshire headquarters to examine and evaluate the interaction of ink and other substances with its print heads. Ink and chemical manufacturers send materials to this lab to determine their compatibility with specific print heads. Dimatix AMD examines inks and the print heads, in which they flow, with advanced testing and examination devices.

    These include:

    • Scanning Electron Microscopes (SEM), along with Electron Dispersion Spectometry (EDS), produce extremely high-resolution images of extremely small phenomenon by scanning an electron probe across a surface. Mary Hoisington, Director of AMD, says “Fujifilm Dimatix has a LEO Field Emission (FE) Scanning Electron Microscope and a PGT EDS detector. The FE SEM allows for high-resolution imaging and utilizes secondary and back-scattered electrons for imaging. The maximum magnification of our system is 1.5 million times the magnification of the human eye. At this high magnification, the resolution capability between two points is 1.5 nanometers at 20 KV accelerating voltage. The limit of detection is specified as 0.1-percent to 1-percent level, with a depth resolution of 2-6 nm.” These instruments enable AMD to examine the shape or morphology of particles and surface phenomenon, and determine the size and dimensions of subject items as compared with the standards. Monitoring sec ondary X-rays that result from the interaction of the electrons and specimens produces detailed maps of elemental distribution, which enable the identification of specimen chemical composition.
    • Fourier Transformation Infrared Spectroscopy (FTIR) is a tool for identifying organic molecules, including polymers, plastics, organic films, fibers, liquids and some inorganic molecules. It uses infrared-light absorption detection to generate the IR spectrum of the specimen, which can provide information about its molecular structure and chemical bonding characteristics. Dimatix uses a Thermo Nicolet FTIR with a bench-top Attenuated Total Reflectance (ATR) system and microscope attachment. These systems have enabled Dimatix to amass a library of spectral signatures for known materials used in print heads and related systems, which enables the company to distinguish organic contaminants as small as a 10 micrometer diameter particle.
    • Gel Permeation Chromatography (GPC) enables the AMD to determine the purity and rheology of polymers dissolved in a known solvent. Dimatix uses a Polymer Laboratories GPC solely for quality control analysis of epoxy chemistry that it uses in its Generation 2 print heads.
    • Differential Scanning Colorimeter (DSC) measures the heat flow of materials that are gradually heated. AMD uses a Perkins-Elmer DSC to monitor its own epoxy formulations.
    • Non-contact Profolimeter enables AMD to measure specimens without destroying them and to determine surface roughness, film thickness and 3-D profiles for nozzle plates, PZT and Flexprints. It uses a Zygo-white light interferometer for examining these materials and setting specifications
    • The Keyence Digital Microscope AMD uses will magnify 3,000 times the capabilities of the human eye. It enables the examination, video recording, measuring and 3-D mapping of specimens. Its high-definition camera and 18 megapixel CCD allow for finer imaging than what is available from existing optical microscopes.

    Dimatix AMD uses its capabilities for qualifying ink and chemical manufacturers’ chemistry, investigating print head operation and failure, as well as monitoring chemistry that Dimatix uses in its manufacturing processes. Dimatix certifies specific inks to perform with each of its print heads. It also has designated a number of leading ink manufacturers as ink partners, but many partner inks are not certified. Dimatix ink partners include: Chemigraf Iberica S.L., DuPont InkJet, EFI Inkware, Fujifilm Sericol UK Ltd., Hexion Specialty Chemicals Inc., Konica Minolta Medical and Graphic Inc., Sensient Imaging Technologies Inc., SunJet and Tentenal AG & Co. KG.

    Other major print head manufacturers have similar testing and evaluation capabilities. Xaar also has developed a counterfeit resistant hologram for use on packaging it certifies to reassure end-users. Xaar intends that it will differentiate approved inks from non-approved ink, and create a deterrent against the likelihood of counterfeiting, tampering and unauthorized distribution of approved inks. Dr. Jill Woods, Xaar’s Ink Product Manager, administers Xaar’s hologram.

    Xaar’s ink partners include: Agfa, Fujifilm Sericol UK Ltd., Hexion Specialty Chemicals Inc., Hilord Chemical Corp., Sensient Imaging Technologies Inc., Staedtler Mars GmbH & Co. KG, SunJet, Toyo Ink Europe, S.A. and Xennia Technology Ltd.

    Increasing Competition for the Inkjet Ink Aftermarket
    Major ink companies that supply inks to OEMs are beginning to offer their inks to the aftermarket that they currently do not serve. Since these companies often make ink for the same print heads as OEMs that do not use their inks, major ink companies have begun to target each other’s OEM users with Fourth-party inks.

    For example, Sun Chemical announced a line of solvent inks for an HP Scitex printer that uses Ricoh print heads. It also supplies another OEM that uses Ricoh heads. Major inkjet ink manufacturers, such as NazDar and INX Triangle, have developed their businesses primarily in the aftermarket, but also have OEM clients.

    The increase in competition will likely lower the price of inkjet ink, while providing the quality controls and research and development investment associated with major ink suppliers. This will likely push low quality suppliers out of the market. However, consolidation of OEM companies could moderate any ink price decline.

    This article appeared in the SGIA Journal, 4th Quarter 2007 Issue and is reprinted with permission. Copyright 2007 Specialty Graphic Imaging Association (www.sgia.org). All Rights Reserved.

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